Field of the Invention
The present invention generally relates to treating and preventing diseases of the cornea and, more particularly, toward apparatuses and methods for releasing free radicals and/or for causing a cross-linking of the collagen by photoactivating a therapeutic agent.
Description of Related Art
Corneal Collagen Crosslinking (CXL) is a treatment of the cornea in which a chromophore, for example Riboflavin eye drops, is applied, and then Ultraviolet (UV) radiation impinges on the cornea to increase collagen cross-links. Currently, the CXL treatment is being clinically tested to determine if it can be effectively used to treat primary (keratoconus) and secondary (iatrogenic keratectasia) ectatic diseases of the cornea and infectious (bacterial, viral, fungal and parasitical) and non-infectious corneal melting. Specifically, the combined application of Riboflavin and UV exposure causes a cross-linking of the collagen increasing the mechanical strength of the cornea. Also, it may eliminate infectious microbial, fungal and parasite agents that cause these infections presumably by generating free radicals that disrupt. Further, the combined application of Riboflavin and UV exposure increases the stromal resistance against enzymatic digestion through steric hindrance. Similarly, the changed physiology caused by the cross-linking may prevent organisms from getting into deeper tissue portions
Application of UV radiation to human tissue is potentially harmful, since over-exposure may damage ocular tissues.
In WO 2009/042159, a wearable photoactivator for ocular therapeutic applications is disclosed. The device comprises a wearable frame to which a light source housing is attached. In embodiments, different lenses of different sizes can be brought into position, and an infrared source-phototransistor pair can be used to detect which of the lens sizes is in position. The radiation source controlling current can depend on the phototransistor signal. The radiation source may further comprise a rear facet photodetector or similar to provide constant power output.
UV radiation, if applied with too strong intensities or under wrong circumstances, can have a damaging effect. A disadvantage of the photoactivator of WO 2009/042159 is that the correct operation depends on the settings the ophthalmologist chooses. Therefore, a photoactivator as taught in WO 2009/042159 can only be used by specialized and well trained ophthalmologists.